Deflection dynamometer



, June 9, 1936.

E. R. HARRALL ET AL DEFLECTION DYNAMOMETER Filed March 17, 1934 uINVENTQRS E. R. HARRALL BY PARROTT AT oRNEY Patented June 9, 1936 i l yl n v UNITED STATES" PATENT OFFICE 2,043,953j l v f 'i f n,

nEFLEC'rloN nYNAMoME'rEn Edwin R. Harrall, Englewood, and Robert D.Parrott, West New York,-N. J., assignors Vto The Western UnionrTelegraph Company, New York, N. Y., a corporation of New YorkApplication Maren 17, 1934, serial No. 716,132

` 11 claims. 01. zes-1.6) Y- i This invention relates to devices formeasuring Another object is to provide means for varying stresses inelements susceptible to transverser dethe stiffness of the stressmeasuring spring so as nection. It relates primarily to means formeastochange the effective range of the instrument.- uring deflection inmembers under stress such as Another object is to provide means, 1inconnec- 5 wires, cables, ropes andthe like and for determintion with thehook at' one end of the beam or 5 ing the tension stresses in suchmembers `as a4 framework, which will prevent the instrument( function ofthe stresses measured by the device. .from falling from a line or strandover which These devices are ordinarily known as deflection the hook hasbeen placed. dynamometers or tensiometers and involve means Anotherobject is to provide kmeans which will l for producing a predeterminedtransversedeflec# also be advantageous in fastening the instrument 1otion in a predetermined length of the strand and or device to the personof the user such'as to the means for measuring the force required toprolinemans belt. j duce the deiiection. l f n Still another' object isto provide means, in con- Dei'lection dynamometers of the type to whichnection with thehook at the other end ofthe l5 thisinvention relatesusually lembody a suitable framework, for properly alining the wire orstrand 15 framework having means to engage a predeterwith respect to itsContact with the spring memmined length of a strand ordinarily at threeber as the instrument is placed in tension measpoints with means forforcing the vengaged pcruring position on the strand. tion out of itsnormal longitudinalalinement by Still another object is to provide anarrangesetting one of the force producing elements to act ment forplacing the indicating mechanism exter- 20 in opposition to the othertwo. Ordinarily the nal of the elliptical spring so thatits spring maymeans engaging the strand at the outer points are be constructed with arelatively small minor axis. termed the arms and the means engaging theThese and other objects will be apparent from strands at the centralpoint is termed the fulcrum. the Afollowing description and claims takenin con- In order to measure the force required to setupy-nection withthe accompanying drawing, in g5 the deflection in the strand a spring oran equivawhich: lent stress measuring memberis associated either Fig. 1is a view in elevation of theidevice; with the fulcrum or one of thecontact arms. The Fig. 2 is a view taken along line 2-2 of Fig.' 1 mostcommon type of deection dynamometer with the details of the armsomitted;

involves a beam of a given length having a spring Figs. `3, 4 and 5 areviews showing details of the 30 or other yieldable member for actingagainst they arms at the left and right ends; and fulcrum and means forapplying a deecting force Fig. 6 is a fragmentary detail view of a.modified to the fulcrum comprising either the spring alone form ofspring. y l under stress or means for moving the fulcrum Heretofore inconstructing' a deiie'ction dysupport with respect to the beamfforapplying namometer the general object appears to have 35 through thespring the deflecting force. In subbeen to construct a device having asubstantially stantially every case the deilecting force is deuniversalapplication` to measuring tensions in termined by measuring the movementl of the wires,.cables, ropes and the like of a wide variety spring oryielding member which is proportionate vof sizes `and stresses. As aresult the devices sok 40 tothe resistance of the strand to deflection.This vconstructed have been ,rather complicated and 4o resistance todeflection is likewise in proportion to delicate in nature and at thesame time high in the tension of the strand from which may be cost.determined the actual tension stresses uponl the It is the purpose ofthis invention to provide a strand. device of extremely simpleconstruction which The principal object of this invention is to pro-.may be made of rugged and inexpensive parts and 45 vide a deflectiondynamometer of simple, rugged, which will at [the same time measuretensions and inexpensive construction which at the same within apredetermined range with extreme accutime has a high degree of accuracywithin the racy. With the type oi device herein to be de; limits of itsintended operation. scribed, owing to its low cost per unit, apredeter#lAnother object of this invention is to provide mined relatively widerange of circumstances may 50 a simple and rugged spring ofapproximately be covered by a number 0f units at even less costelliptical form which may be easily assembled than a single instrumentfor universal applicaand attached firmly to the frame or beam of thetion. `Where the tensions to be measured 'and device and which willsatthe Sametime `retain its the wires or strands involved are withinrelatively accuracy over long periods of use. narrow limits,`it isobvious that the user'is not 55 put to the expense of a complicatedcostly instrument.

According to a modication of the invention a simple means is providedfor changing the stiffness of the fulcrum spring for extending the rangeof the instrument within certain limits.

For a better understanding of the invention reference will now be had tothe drawing showing the invention. In its preferred embodiment thedevice comprises a framework embodying a beam member I0 having itsopposite ends turned upwardly to form hook arms II and I2. The arms IIand I2 embocw hooks I3 and I4 respectively, (Figs. 3 and 4), which mayengage a section of the wire I5, the tension of which is to be measured,at spaced points equivalent to the length of the beam I0. 'I'he deviceis illustrated in Fig. 1 as about to embrace the wire I5.

Mounted centrally upon the arm I 0 is a spring I6 of approximatelyelliptical form, the upper portion of which is arranged to engage theembraced section of the wire at its central point and form the fulcrum.'I'he spring has a height suillcient to cause the wire engaging portionto normally stand at a predetermined position beyond a straight lineconnecting the hooks I3 and Il at the opposite ends of the beam.Therefore, when the instrument is placed upon a section of wire so thatthe embraced portion passes from the hook It over the-center of thespring I6 to the hook I3 it will be deflected out of a straight lineposition by the force of the spring. 'I'he wire tending to assume astraight line position will force the spring down until there is abalance reached between the resistance of the spring and thestraightening effort of the wire. 'This point of balance will occur atvarious compressions of the spring, always in proportion to the tensionof the wire.

Referring particularly to Figures 1 and 2 the spring I6 comprises aplurality of preshaped elements which may be-made from regular stockbars of spring steel or the like of suitable dimensions. The elementsare an upper leaf I1, extending the full length of the spring, and asplit lower leaf forming two halves Il and I9. The upper leaf is shapedwith its central portion boved upwardly and its ends extending outwardlyin horizontal alinement. The lower leaf comprises two sections III andI9. They generally conform in shape to the upper leaf so that the wholespring assembly may ex as a unit substantially free from longitudinalstress. The at or horizontal outer end portions of the sections I 8 andI9 are secured to the upper leaf I1 by means of rivets 2l or othersuitable means. The inner ends of the sections are spaced apart asufficient distance to admit the plunger 22. The inner ends embody ashort hat section which is secured rigidly to the beam Ill by means of apair of rivets 23 or other suitable fastening means.

By providing a spring of a plurality of parts rigidly secured togetherand rigidly secured to the beam of the framework, a spring assembly isobtained which embodies substantial transverse rigidity with respect tothe frameworkY and which is at the same time readily yieldable in itsplane of action and suiliciently sensitive to incorporate a high degreeof accuracy. Accuracy also results from the simplicity of the partscomprising the spring and the simple and accurate method of assembly ofthe parts. A spring of a type herein describedembodying substantialtransverse rigidity is less apt to slide from beneath the wire when theinstrument is being placed thereon.

'Ihls is a distinct advantage over less sturdy types of springs whichare removably mounted to the framework or are mounted upon a movableelement by means of which the spring is to be adjusted with respect tothe beam of the framework. 5

According to the modification of this invention,

a fragmentary view of which is shown in Fig. 6, the range of the springI6 may be changed so that the instrument will act properly to measurethe tension in wires and cables of substantially dif- 1o ferent sizes.In the preferred form of the modification the change is accomplished byemploying bolts 2i in place of the rivets 2I employed in Fig. 1 so thatthe upper leaf of the spring I1 may be replaced by a leaf Il having agreater or less 15 thickness which will increase or decrease thecombined stiffness of the spring according to whether it is desired toextend the range upwardly or downwardly from the original range of thedevice. It is noted that this modification 20 does not alter or changethe simplicity of the device and the ruggedness and accuracy of theconstruction. n

Obviously, the range of the spring I6 may be changed in various otherways such as by adding 25 leaves of any desired thickness to theoriginal leaf I1 of thespring. It may also be changed by employing boltsin the place of rivets 23 in the preferred embodiment illustrated inFig. 1 so that the entire spring may be removed and a 30 spring of adifferent scale substituted therefor. It is to be noted in this case,however, that it will be necessary to make either the plate 24 or 25 orboth easily removable so that access may be had to the bolts which wouldfasten the spring 35 to the beam. Obviously, other means of variation ofthe scale or range of the spring will occur to those skilled in the artand which will avoid the error of prior art devices of providing athrust action spring having insufficient transverse 40 rigidity.

In order to protect the spring when the instrument is in use and toassist in guiding the wire to be tested, side plates 24 and 25 arearranged to extend upwardly from the beam to cover the 45 centralportion of the spring. The upper edges of the plates extend beyond thenormal extended position of spring to form guide members for the wire.The plates are usually positioned close to the sides of the spring so asto prevent the wire 50 from entering the space between the plates andthe edges of the spring. In order to make the upper edges of the plateadjustable with respect to their distance from the spring, screws 26 orother suitable adjusting means may be provided'55 for drawing the platestogether.

It will be observed that according to this invention the dial orindicator mechanism is located entirely externally of the measuringspring I6. This enables the spring to be con- 50 structed with arelatively short minor axis giving a greater compactness andflexibility. It will be observed also that the connection with themovable portion of the spring is provided in the most direct manner,that is, by providing an opening in the stationary side of the spring toadmit the stem 22 which projects across the minor axis of the spring.and connects the movable side with the dial indicator operatingmechanism. This o type of an arrangement is particularly adapted topermit the use of any suitable type of standard make of dial indicatorsuch as those known in the art as thickness gages or indicators. Withthe type of arrangement just described no spcial 15 apparatus isrequiredr- All of the parte may be made of standard materials.

Since the movement of the spring, as already has been stated, is inproportion to the tension of the wire, likewise the readings of the gagewhich are determined by the movement of the spring are in proportionalso. Therefore the dial of the gage may be calibrated to readthetension of the wire direct where the instrument is to be applied to thesame type of wire at all times. If it is desired to apply the instrumentto different types of wire, the ldial of the gage may be calibrated withan arbitrary scale such as equal divisions. The latter is the formillustrated in the drawing and preferred in the present embodiment;I Acalibration chart or curve is prepared when the arbitrary scale is usedso that the dial readings may be readily transferred to tension units,preferably pounds, corresponding to the wire being measured.

The gage 21 is illustrated as having a dial 28 and a hand 2S. 'I'he dialis calibrated to indicate thousandths of an inch in the movement of theplunger 22. The gage is mounted in a protecting housing 30 secured rtothe llower side of the beam I0. The housing preferably includes a solidback plate to which the gage is/ secured by any vsiutable fasteningmeans. and an open front. It is preferred that the upper end-of theplunger 22 shall be spaced slightly from the normally extended positionof the spring I6 so as to insure that the hand of the gage will alwaysreturn to zero when the instrument is not in use. A very small spacebetween the stem and the spring does not materially affect the accuracyof the instrument since it is seldom that a tension is so slight as notto bring the spring into engagement with the pin. In all other casesthis space would be compensated for in the calibration of the instrumentand would cause no error in the reading. The advantage of permitting thedial to always return to zero is to prevent attempts of persons notversed in the theory of the operation of the instrument to adjust theinstrument to zero, destroying the accuracy of the accompanyingcalibration curve. Italso largely removes the possibility of unskilledpersons doubting the accuracy of the instrument.

In order to add to the practicabllity and usefulness of the device ithas been provided with the safety clip 3| secured to the upper portionof the arm4 I2 above the slot which forms the hook Il. It extendsoutwardly transversely of the arm in an inclined direction from the noseof the hook. By this arrangement the clip member serves as a guide todirect thewire into the slot I 4 when the instrument is beingmountedupon the same. The outward end of the clip member is bent backward at anincline so as to engage the beam I0 back from the arm I2. The clipmember is preferably comprised of a leaf spring which is formed so thatthe outward end is pressed against the beam. The spring extends beyondthe point where it engages the beam and is bent outwardly so asto'engage the wire `or other rod which is to be passed into the hook.This spring also enables the instrument to be clipped for carriage tosomepart of the clothing of the user, such as a linemans belt. When itis about to be mounted on a wire or rod, the clip is slipped over thewire so that the instrument will be secured safely thereto, even thoughit should slip from the hand of the user while pressing the wire intothe hook Ii'at the other end. Should it slip it will merely'hang ordangle from the wire at the right end. A clip member in the form of aspring provides a readily usable feature together with safety.

Assuming that the device is to be employed for measuring the tension ofa wire strung upon telegraph poles, the user with the instrument heldwith the beam Il in a somewhat vertical direction, catches the wire I5between the outward end of thevclip 3| and the point where it engagesthe beam. He then pulls the instrument downwardly until the wire passesbehind the safety clip. If he so desires he may release or let go of theinstrument at this point and it will hangqupon the wire, being retainedby the action of the safety clip as il well understood. The recess 32 inthe beam into which the outer curved end of thespring' fits adds to theeffectiveness of the clip in preventing the wire from accidentallypassingv out again should the instrument be violently swung while it ishanging loosely upon thev wire.

' The manner in which the instrument may be mounted in position-toindicate the tension will now be described. From swinging position theinstrument is alined as shown in Fig. 1 with the wire resting in thehook I l and passing over the top of the elliptical spring I6 and inposition above the hook I3 formed in the arm II, atthe opposite end ofthe beam. Since the spring I6 is relatively rigid transversely of thedevice, no .dilculty will be experienced in placing the wire in asubstantially central position upon the spring. With the wire in thisposition and preferably with the fingers of the hand clasped around theleft end of the beam I0, the thumb is brought up to catch the wireoutwardly of the arm I I. With the thumb the wire is forced downwardlyalong the cam face 33 formed by the portion of the arm extending beyondthe hook I3. The wire is causedto slide along this cam face until itsnaps into the hook, the instrument then being mounted upon the wire insuch a man. ner that the portion embraced between the two arms II- andI2 is deflectedV by the spring I6 by an amount proportionate to thetension of the.

wire. The resistance of the wire to deflection presses the spring I6inwardly which by its engagement with the stem 22ycauses the pointer 29of the indicator 21 to indicate the movement of the spring. By suitablecalibration tables the readings of the dial can be transferred intoreadings which indicate the tension of the wire.

Referring to Figure 3, the cam surface of the upper portion of the armis formed ina denite relation with the position of the hook, and thecentral point of the upper leaf of the spring I6. The face of thesurface is inclined Ibackwardly from the nose of the hook an amount suchthat, with the wire positioned centrally. of the spring I6 and broughtto a position substantially parallel with the beam III, it will engagethe surface at a point substantially vertically above the hook. When thewire is brought into engagement with the cam surface it will havealready been pressed firmly upon the spring and, even though it mustswing to one side to pass beyond the nose of the hook, there is littletendency for the wire tu be displaced from its central position upon thespring;

Duetov the fact that care must be exercised in avoiding kinks in theportion of the wire embraced between the' hooks I3 and I I, a plate u isplacedso as to extend inwardly from the arm II to insure that theoperator in placing his thumb or hand upon the wire to force it intoposition will grasp the wire on the outside or beyond the arm il ratherthan inside of the arm.

From the above description it will be seen that a tensiometer ordeflection dynamometer has been devised in an extremely simple andrugged form and which may easily and readily be adapted to perform theoperation of measuring tensions or other forces in wires, rods and thelike which may be measured by deecting a predeterminedl length thereof.Due to the simplicity and ruggedness of the device its accuracy will bemaintained under substantially all conditions and will not be materiallyaffected by the type of use to which it is put nor the temperature orweather conditions when employed in exposed localities. In addition adevice constructed according to this invention may be readily used byinexperienced persons.

The details and principles of this invention will readily suggestthemselves for use in various other forms or adaptations as will beapparent to those skilled in the art.

Although this invention has been shown in but two forms, it will beapparent to those skilled in -the art that it is not so-limited, but issusceptible to various other changes and modifications without departingfrom the spirit thereof and it is desired, therefore, 'that only suchlimitations shall be placed thereupon as are imposed by the prior art oras set forth in the appended claims.

What 'we claim is:

l. A tensiometer having a beam embodying hook members at its ends forengaging at spaced points a strand of material, the tension of which isto be measured, a spring of elliptical type embodyng upper and lowermembers, and an ex- 'tensible element disposed to be acted upon by theupper member of said spring as it moves, said lower member being dividedsubstantially at the 'mid point into two parts separately secured to thebeam, said parts being secured with their inner ends spaced apart foradmitting the extensible' element from a point external of the spring,said upper member being rigidly secured to the lower member and arrangedwith its uppermost portion in disalignment with said hook members andpressing upon said strand substantially centrally between said hooks toeffectuate a deflection in said spring.

2. A deflection dynamometer o'f the type having a beam provided withmeans at its ends to embrace a portion of a wire, the tension of whichis to be measured, and a spring of elliptical type rigidly secured tosaid beam, said spring being formed with upper and lower members ofribbon metal stock of ubstantially runiform section, the outer ends of te respective members being secured together so as to form`a spring unit,said unit being secured-so that its uppermost portion is in disalignmentwith said wire embracing means and in position to deflect the embracedportion of the wire by engaging said embraced portion substantiallycentrally thereof.

3. In a deflection dynamometer having a beam carrying engaging membersfor embracing a section of a strand of material to be tested, aresilient fulcrum member secured to the beam between the engagingmembers and arranged to press upon said strand for producing adeiiection thereof proportionate to the stiffness of the fulcrum member,said fulcrum member comprising an elliptical spring, a dial typedeection indicator secured to said beam in a position externallyof saidspring and having an extensible stem, the side of the spring secured tosaid beam being provided with an opening for admitting the stein of saiddeflection indicator to engage a leaf of said spring internally thereofand to permit the longitudinal movement of said stem.

4., In a deflection dynamometer having a beam carrying engaging membersfor embracing a section 'of a strand of material to be tested, aresilient fulcrum member secured to the beam between the engagingmembers and arranged to press upon said strand for producing adeflection thereof proportionate to the stiffness of the fulcrum member,said fulcrum member comprising an elliptical spring, a deflectionindicator secured l5 to said beam in a position externally of saidspring and having an extensible stem, the side of the spring secured tosaid beam being provided with an opening for admitting the stem of adeiiection indicator, said stem being disposed to extend across saidspring to engage the free side when the spring is compressed, said stemand said free side of the spring when in their normal extended positionsbeing separated by a space sufficient to prevent the spring fromengaging the stem when at rest, whereby the pointer of the indicatorwill rest at its full retarded position.

5. In a deflection dynamometer devicevrcr testing rods, strands, and thelike, a beam having upstanding arms adjacent its ends for embracing asection of a strand, an elastic member for deilecting the embracedstrand, hooks provided on said arms, a resilient spring secured to oneof the arms above the hook opening and arranged to extend beyond thenose of the hook for forming a guide member for directing the strandinto the hook as the device is placed thereon.

6. In a tensiometer device for testing wires, cables and the like, abeam having upstanding arms adjacent its ends for embracing a section ofa strand, an elastic member for deflecting the embraced strand, hooksprovided on said arms, a resilient spring secured to one of the armsabove the hook opening and arranged to extend beyond the nose of thehook, the outer end of the spring member being bent backwardly to extendfrom the arm across said beam so as to form therewith a safety clip forinsuring that the device is retained-upon the strand duringmanipulation.

7. In a deiiection dynamometer device for testings rods, strands, andthe like, a beam having upstanding arms adjacent its ends for embracinga section of a strand, an elastic member for deflecting the embracedstrand, hooks provided on said arms, one of said hooks being providedwith a cam guiding surface embodied in a portipn of the arm extendingabove said hook, the cam sur., face of said portion being arranged toincline backwardly from the nose of the hook for guiding the strand intothe hook as it is brought down across the deflection member, saidguiding cam surface being disposed so that as a. strand positionedcentrally of the elastic member comes down to substantially parallelwith said beam, it will engage said cam surface directly above theresting plac of the strand in the hook.

8. In a deflection dynamometer device for testing rods, strands, and thelike, a beam having upstanding hooks formed at `the ends for embracing alength upon which a test is to be made, an elastic spring having a fiattop for engaging the length to deflect the same, one of said hookshaving a portion extending upwardly and backwardly from its nose andembodying a @am sulface for forming a guide and aligning member.

said cam portion being so disposed that the transverse projection of itssurface lies within the projection of the at top of said spring.

9. A tensiometer' having ay beam embodying hook members at its ends,means to embrace a portion of a strand of wire or the like, the tensionof which is to be measured, and a spring of e1- liptical type embodyinga lower member fixedly secured to said beam, said lower member beingarranged to have secured thereto a replaceable upper member whereby theiiexibility of- 'the` spring as a whole may bey changed by inserting anupper member of different stiffness to convert the tensiometer to adiierent scale of measurement. I

10. A tensiometer having a beam embodying arms at its ends for embracingat spacedV points a strand of material, the tension of which is to bemeasured, a spring of elliptical type embodying a iixed lower member anda replaceable upper member, said lower member being secured to said beamat points on either side of its mid-portion and spaced from saidmid-portion, and an extensible element mounted independently of butdisposed to be acted\upon by the upper member of said spring as it isdeflected, guide means for the extensible element for holding it erect,said lower member embodying substantially' at its mid-point an openingfor admitting the extensible element and its guide means from a pointexternally of the spring whereby said upper member may be changed foraltering the range of measurement of ,the tensiometer without dis-rturbing or changing any part of the extensible element.

11. A deflection dynamorneter of the type havelliptical type rigidlysecured to the inner side of f said beam between said arms for forming aresilient fulcrum member arranged to press upon said strand forproducing a deflection thereof measurable by the concomitant deflectionof the fulcrum, a deection indicator secured on the outside of said beamopposite said spring and having an extensible stem, the beam between thespring and indicator and the side of the spring secured to said beambeing provided with an entrance way for admitting said stem, said stembeing disposed to extend from the indicator loosely through said way andacross said spring forl engaging the free side of said spring whereby accmpressional displacement of the spring is transmitted to theindicatorby the longitudinalmovement of said extensible stem.

EDWIN R. HARRALL. ROBERT D. PARROIT.

